Hydrogen peroxide

About: Hydrogen peroxide is a research topic. Over the lifetime, 42583 publications have been published within this topic receiving 1043732 citations. The topic is also known as: H2O2 & dioxidane.

Iron Redox Cycling in Surface Waters: Effects of Humic Substances and Light

Abstract: The purpose of this study is to examine the mechanism of photo-oxidation of natural dissolved organic matter (DOM) in the presence of iron. This process is of interest in natural waters for several reasons: as a significant sink of DOM in sunlit surface waters; as a source and sink of reactive oxygen species (HO2/O2•-, hydrogen peroxide, and HO•) and as a factor controlling iron speciation. Studies were conducted in laboratory model systems containing fulvic acid and lepidocrocite (γ-FeOOH) particles at pH 3 and pH 5, irradiated with simulated sunlight. Measured concentrations of dissolved Fe(II), total dissolved Fe, and hydrogen peroxide were interpreted as the net effects of competing reactions reducing and oxidizing Fe and producing and destroying hydrogen peroxide. A kinetic model constructed using information gained from separate experiments in simpler systems was used to assess the relative importance of individual reactions. Comparison of photoreductive dissolution rates in aerated and de-aerated ...

OxyR and SoxRS Regulation of fur

Abstract: The cytotoxic effects of reactive oxygen species are largely mediated by iron. Hydrogen peroxide reacts with iron to form the extremely reactive and damaging hydroxyl radical via the Fenton reaction. Superoxide anion accelerates this reaction because the dismutation of superoxide leads to increased levels of hydrogen peroxide and because superoxide elevates the intracellular concentration of iron by attacking iron-sulfur proteins. We found that regulators of the Escherichia coli responses to oxidative stress, OxyR and SoxRS, activate the expression of Fur, the global repressor of ferric ion uptake. A transcript encoding Fur was induced by hydrogen peroxide in a wild-type strain but not in a DeltaoxyR strain, and DNase I footprinting assays showed that OxyR binds to the fur promoter. In cells treated with the superoxide-generating compound paraquat, we observed the induction of a longer transcript encompassing both fur and its immediate upstream gene fldA, which encodes a flavodoxin. This polycistronic mRNA is induced by paraquat in a wild-type strain but not in a DeltasoxRS strain, and SoxS was shown to bind to the fldA promoter. These results demonstrate that iron metabolism is coordinately regulated with the oxidative stress defenses.

Efficient manganese catalysts for low-temperature bleaching

Abstract: THE detergents of the next century will be routinely required to contain bleaching agents that are not only more active than those currently available but also environmentally safe and cost-effective. Hydrogen peroxide, the traditional bleaching agent1, loses its activity as the washing temperature decreases. Peroxyacetic acid maintains acceptable bleaching activity down to 40–60 °C (ref. 2), but still lower temperatures are desirable. It is generally recognized that manganese and iron complexes are less environmentally damaging reagents than other transition-metal compounds, and such complexes have received considerable attention as bleaching catalysts3–11. Here we show that manganese complexes derived from l,4,7-trimethyl-l,4,7-triazacyclononane and related ligand systems act as highly effective catalysts for the bleaching of stains by hydrogen peroxide at low temperatures. These complexes also catalyse the epoxidation of alkenes and the oxidation of poh phenolic substrates by hydrogen peroxide. Our results demonstrate the considerable potential of these systems for clean and efficient low-temperature bleaching.